Field of the Invention
The present invention relates to integrated circuits which include flash memory arrays or other non-volatile memory arrays, with security features that utilize a unique key or unique identification code.
Description of Related Art
Integrated circuit memory devices comprising non-volatile memory, such as flash memory, are being developed with very high capacities. Some technologies are considered likely to enable terabit scale arrays on integrated circuits. Also, memory devices are being deployed in so called “internet of things IoT” devices, interconnected by networks that operate with, for example, internet protocol communications technologies. A concern for IoT devices and other devices that store data, is data security. Thus, security protocols requiring encryption with unique keys, authentication with unique IDs and challenge/response technologies are being deployed.
Security protocols require key management technologies to generate, update, store and protect the unique keys and IDs utilized.
A physical unclonable function (PUF) is a process usable to create a unique, random key for a physical entity such as an integrated circuit. Use of a PUF is a solution for generating keys used for chip IDs supporting a hardware intrinsic security (HIS) technology. PUFs have been used for key creation in applications with high security requirements, such as mobile and embedded devices. An example PUF is a ring-oscillator PUF, that uses the manufacturing variability intrinsic to circuit propagation delay of gates. Another example PUF is an SRAM PUF, where threshold voltage differences in the transistors result in the SRAM powering up in either a logic “0” or logic “1”. See “Physical Unclonable Functions and Applications: A Tutorial” by Charles Herder et al., Pages 1126-1141, Proceedings of the IEEE|Vol. 102, No. 8, Aug. 2014.
A PUF that uses the physical property of resistive random access memory has been proposed. See “A ReRAM-based Physically Unclonable Function with Bit Error Rate <0.5% after 10 years at 125° C. for 40 nm embedded application” by Yoshimoto et al., Pages 198-199, 2016 Symposium on VLSI Technology Digest of Technical Papers. The application presented in the paper proposes an improvement on the conventional ID-generating method of ReRAM-PUF which increases bit error rates due to aging degradation. However, in this ReRAM-based PUF, the data created can still be corrupted by drift in the resistance of the memory cells, which can make a bit error rate unacceptable when accessing or using the stored key. Such resistance drift can be more pronounced at high temperature encountered in some applications of integrated circuits, such as in automotive applications.
When using data sets generated using PUF circuits, prior art technologies have relied upon error correcting codes to improve reliability because of the problems with high bit error rates. See, for example, Lee et al., U.S. Patent Application Publication No. 2016/0156476, “Physically Unclonable Function Circuits And Methods Of Performing Key Enrollment In Physically Unclonable Function Circuits,” published Jun. 2, 2016.
It is desirable to provide technology for integrated circuits including non-volatile memory that support the use of PUF generated keys and other unique keys.